The present invention generally relates to orthodontic devices and, more specifically, to intra-arch devices for treating malocclusions.
Orthodontics is a branch of dentistry which deals with correcting irregularities in the arrangement of teeth, including the crowding of teeth and excessive spacings between nearby teeth. Orthodontic devices for treating such malocclusions are well known in the field of dentistry. Traditionally, orthodontic devices used for the movement of teeth to treat malocclusions includes a force-applying element that provides a continuous corrective force between one or more orthodontic pads, brackets or bands attached to a patient""s teeth. The corrective force urges the teeth to move in a predetermined direction to correct the crowding or excess spacings. In some instances, orthodontic devices are used in intra-arch applications in which one or more teeth are moved relative to other teeth of the same jaw. In other instances, orthodontic devices are used in inter-arch applications in which one or more teeth or an entire dental arch is moved relative to the opposite dental arch.
The attachment of the orthodontic device usually involves the attachment of brackets to the teeth, either by adhesive bonding or the securing of bands around the circumference of various teeth. The brackets are usually each provided with a slot through which an arch wire is extended. Generally, one force-applying element is provided for the teeth of the upper jaw and one for the teeth of the lower jaw. The force-applying elements of conventional orthodontic devices are generally positioned on the labial side of a patient""s teeth to avoid uncomfortable interference with the tongue. One type of force-applying element is an arch wire that is deformed and bent into a shape to attach to the brackets so as to supply the corrective force. Other force-applying elements include elastomeric bands, compression springs, and extension springs that are attached between adjacent brackets for the purpose of supplying the directional corrective force to move the teeth.
Arch wires have various shortcomings as force-applying elements. When the device is installed, the arch wire is shaped such that the arch wire applies an appropriate amount of corrective force in an suitable direction effective to move the teeth in the predetermined direction. During the course of a patient""s treatment, the clinician periodically manually readjusts the device, usually by reshaping or bending the arch wires, to adjust the corrective force. Clinicians often have difficulties in creating these complex and precise bends in arch wires, which if not optimized, may compromise the quality of a patient""s treatment and prolong the duration of that treatment.
Elastomeric bands have proven unsatisfactory as force-applying elements because the applied force degrades after only a few hours of exposure to the natural fluids inside a patient""s mouth. Elastomeric bands also supply a displacement-dependent, non-constant force over a given range of motion as the teeth are moved into their new positions in the mouth. Another disadvantage is the patient can remove elastomeric bands so that the outcome of the orthodontic treatment is dependent upon patient cooperation. Elastomeric bands also fatigue such that the corrective force becomes too low to move the teeth efficiently or the bands may even break. As a result, the elastomeric bands must be frequently replaced or adjusted.
Traditional orthodontic devices which employ compression or extension springs also exhibit various deficiencies as force-applying elements. For example, the springs are exposed and the spring coils can pinch the tissue inside the patient""s mouth as the spring expands and contracts. The pinching produces discomfort. In addition, food and other particles may be captured by the spring coils device and result in hygiene problems. Orthodontic devices utilizing steel springs have also tended to be rather complex, as typified by, for example, U.S. Pat. No. 5,299,935 to Lokar. Some prior art devices have utilized covers on the springs, such as U.S. Pat. No. 3,618,214 to Armstrong, but these devices have generally been designed for inter-arch use. Other devices, such as U.S. Pat. No. 5,562,445 to DeVincenzo et al., have utilized telescoping rods with the springs. These devices, however, have generally been designed to correct mandibular/maxillary detentions rather than merely repositioning teeth. Furthermore, these devices necessarily bridge more than one quadrant of a person""s mouth.
Another significant problem with conventional orthodontic devices is that they generally do not apply a pure translational force to a tooth to which it is attached and, as a result, the tooth may rotate or tip as it translates to its new position. This problem arises because conventional orthodontic devices apply the corrective force at a tooth attachment point that does not necessarily coincide with the center of resistance of the tooth.
Accordingly, there is a need for a compact intra-oral orthodontic device, which is capable of translating a tooth without significant rotation and which is not susceptible to pinching the patient or allowing food or other particles to be trapped by the device.
The present invention provides an intra-arch orthodontic device for adjusting the distance between a first tooth and a second tooth located in a single quadrant of a mouth. The device includes a guide tube, an elongated member, and a spring positioned in an enclosed space provided by the engagement of the elongated member with the guide tube. The guide tube has a first end, an open second end, a hollow interior, and a first longitudinal axis extending along the hollow interior between the first end and the second end. The first end of the guide tube is adapted to be mounted to the first tooth. The elongated member has a third end, a fourth end, and a second longitudinal axis extending between the third end and the fourth end. The third end of the elongated member is slidably received within the second end of the guide tube to form the enclosed space. The fourth end of the elongated member is adapted to be mounted to the second tooth. The spring is positioned in the enclosed space and the spring biases the elongated member relative to the guide tube in a direction substantially parallel to the first and the second longitudinal axes. The magnitude of the biasing force applied by the spring is sufficient to adjust the distance between the first tooth and the second tooth when mounted thereto. The device can be configured to apply a biasing force that provides either a contraction or expansion of the spacing between adjacent teeth. A removable activation structure may be provided which is adapted to hold the elongated member and the guide tube in a locked condition until the activation structure is removed to provide a released condition in which the biasing force is applied.
The invention further contemplates a method for adjusting the spacing between at least the first and second teeth of a patient to a desired spacing using an orthodontic device as generally described above. The method comprises adjusting the distance between a first end and a second end to correspond to the spacing between the first tooth and the second tooth. The distance between the first end and the second end is locked by placing the activation structure in a locked condition. The first end and the second end are affixed to the first tooth and second tooth, respectively. The activation structure is placed in a released condition to apply a biasing force between the first tooth and the second tooth.
One advantage of the present invention is that by bonding directly to the teeth, the device does not require the use of an arch wire. Therefore, the device may be installed on either the labial or the lingual side of the teeth. Another advantage of the present invention is that the flexible connection between the mounting pads and the tube or pin arrangement allows the device to accommodate the natural arch of a patient""s teeth. Another advantage of the present invention is that it permits pure translation of a tooth desired to be moved without the undesirable rotation of the tooth that is typical of existing orthodontic devices. The device of the present invention may be attached at or near the center of resistance of the tooth so that rotation is avoided as the teeth move under the influence of the applied corrective force.
These and various other objectives, advantages and features will become more readily apparent to those of ordinary skill in the art, upon review of the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.